The invention relates to glass compositions which are suitable for making face-plates of cathode-ray tubes used for displaying television pictures, particularly for displaying colour television pictures, to a cathode-ray tube face-plate consisting of such a glass, and to a cathode-ray tube for displaying colour television pictures and having such a face-plate.
Glasses for cathode-ray tube screens must inter alia satisfy the following requirements: a high degree of absorption of electromagnetic radiation, no discoloration by electron beams and a proper fusibility. Chemical Abstracts 88, 175983 s, (1978) discloses a glass which offers a satisfactory compromise as regards the above-mentioned requirements. The known glass contains 58-65 SiO.sub.2 ; 0.5-0.8 Al.sub.2 O.sub.3 ; 6-9.5 Na.sub.2 O; 7-10 K.sub.2 O; MgO.ltoreq.3; CaO.ltoreq.3; SrO 8-10; BaO 3-7; ZrO.sub.2 2-5; F.ltoreq.1; CeO.sub.2 0.1-0.5 and Sb.sub.2 O.sub.3 +As.sub.2 O.sub.3 .ltoreq.1. This glass is very satisfactory as regards X-ray absorption. However, as regards discoloration by electron bombardment there is still room for improvement. The known glass contains F which is unwanted as it is detrimental to the environment.